Bluetooth Network Security

Published on Nov 23, 2015

Abstract

Wireless communications offer organizations and users many benefits such as portability and flexibility, increased productivity, and lower installation costs. Wireless local area network (WLAN) devices, for instance, allow users to move their laptops from place to place within their offices without the need for wires and without losing network connectivity.

However, risks are inherent in any wireless technology. The loss of confidentiality and integrity and the threat of denial of service (DoS) attacks are risks typically associated with wireless communications. Specific threats and vulnerabilities to wireless networks and handheld devices include the following:

 All the vulnerabilities that exist in a conventional wired network apply to wireless technologies.

 Sensitive information that is not encrypted (or that is encrypted with poor cryptographic techniques) and that is transmitted between two wireless devices may be intercepted and disclosed.

 Sensitive data may be corrupted during improper synchronization.

 Data may be extracted without detection from improperly configured devices.

Security Aspects in Bluetooth

The Bluetooth-system provide security at two level-

 At Link layer

 At Application layer

Link layer security

Four different entities are used for maintaining security at the link layer: a Bluetooth device address, two secret, keys, and a pseudo-random number that shall be regenerated for each new transaction.

The four entities and their sizes are summarized in Table-

L2CAP: enforce security for cordless telephony.

RFCOMM: enforce security for Dial-up networking.

OBEX: files transfer and synchronization.

The encryption key in Bluetooth changes every time the encryption is activated, the authentication key depends on the running application to change the key or not. Another fact regarding the keys is that the encryption key is derived from the authentication key during the authentication process. The time required to refresh the encryption key is 228 Bluetooth clocks which is equal to approx. 23 hours. RAND or the random number generator is used for generating the encryption and authentication key. Each device should have its own random number generator. It is used in pairing (the process of authentication by entering two PIN-codes) for passed keys in the authentication process.

Security modes in Bluetooth

In Bluetooth there are three security modes which are:

 Mode 1: Non-secure.
 Mode 2: Service level security

Trusted device

Un-trusted devices

Unknown devices

 Mode 3: Link level.

The trusted device is a device that has been connected before, its link key is stored and it‟s flagged as a trusted device in the device database. The un-trusted devices are devices that have also previously connected and authenticated, link key is stored but they are not flagged as a trusted devices.

The unknown devices are the devices that have not connected before. In Bluetooth service level we have three type of service in regard to the security:

 Services that need authentication and authorization: this is automatically granted to the trusted devices but for the un-trusted devices manual authentication is required.

 Services that need authentication only: in this case the authorization process is not necessary.